1. Field of the Invention
The present invention relates to the use of proteins contained in milk serum. It relates more particularly to a process enabling the production from milk serum of foam products, which are consumable by man as food products.
The invention also relates to the foam products obtained thereby, and to the foods made therefrom.
2. Description of the Prior Art
Milk serum, a byproduct of the cheese industry has long been considered as a bulky liquid effluent of little value, of which only a small portion was kept for animal feeding.
In recent years, the battle against pollution and the search for proteins for food materials, have led the industry to use the proteins of milk serum more and more in the manufacture of foodstuffs.
Thus, milk serum is employed today in animal feeding, in bread making, in pastry making, in pork butchers products and in beverage manufacture.
As a document illustrating the prior art in the field of the valorization of milk serum for the food industry, the article of MANN [E. J. Dairy Industries August (1974) and September (1974)] may be mentioned.
Among the uses suggested, it has been proposed to exploit the foaming properties of the proteins of milk serum to replace the proteins contained in egg white, which are expensive and which are presently used in pastry manufacture for making cakes such as notably meringues, marshmallow, nougat or the like.
The milk serum containing substances which prevent the foam formation from the proteins that it contains, it cannot be used as much as such and requires preliminary processing.
It has been proposed in JELEN P., J. of Diary Science 56, (12), (1973) to remove a portion of the proteins of the milk serum by precipitation of the latter at a temperature of 95.degree. C. at a pH of 4.5, and then taking up the supernatant liquor, concentration, removal of lactose by crystallization in the cold and decantation.
Another process described in Mc DONOUGH F. E., HARGROVE R. E., POSATI L. P. ALFORD J. A. J. of Diary Science 57 (12), (1974), consists of the ultrafiltration of the milk serum, then of a heating step at a temperature above 65.degree. C. at a pH comprised between 5 and 8 to reach a protein concentration equal to 50%.
KUEHLER C. A. and STINE C. M. J. of Food Science 39, (1974) have proposed a process for the treatment of milk serum by filtration on a gel of the latter and subsequent enzymatic hydrolysis.
In Netherlands Milk and Diary Journal--Vol. 29 (1975) pages 198-211, J. DE WITT et al, there is described the ultrafiltration of whey or milk serum from cheese making, and the study of some functional properties of the protein concentrates of the serum resulting therefrom (ultrafiltration retentate). The preparation of a product having particular organoleptic properties has not been sought. The protein concentrates obtained by ultrafiltration of whey or milk serum, have a content of said proteins equal to 48.5%.
In the Netherlands Milk and Dairy Journal publication, the study carried out bears on protein concentrates of whey, that is to say on protein concentrates obtained by ultrafiltration of serum, and constituting the retentate outlined in the course of the ultrafiltration.
It follows necessarily that the products treated according to the process of the invention or subjected to the different analyses of the publication mentioned, are not of the same nature since according to the invention the content of proteins of the milk serum treated is of the order of 2 to 15%, whereas in the Netherlands Milk and Dairy Journal it is indicated that the protein content is equal to 48.5%.
British Pat. No. 670,450 (J. LENDERINK) relates to a process for the manufacture of products based on albumin capable of forming foam, and their application in foodstuffs.
This process consists of mixing a suspension or a solution of proteins previously hydrolysed with a hydrolysing agent other than an alkaline earth hydroxide, said solution or suspension containing both a substantial proportion of polypeptides and of non-hydrolysed proteins, with a calcium based compound capable of forming calcium ions in said solution or suspension.
The treated products are different since the process of British Pat. No. 670,450 relates to the casein, the lactalbumin of the milk serum which have a well-determined composition, which is not to be confused with the milk serum treated according to the present invention.
In addition, in the process described in this patent, the precise treatment is not mentioned except that the use of an alkaline earth base is not required. In particular, it will be noted that reference is made to hydrolysis in an acid medium which is not defined, no condition of time, of pH or of temperature being mentioned.
In addition, U.S. Pat. No. 2,765,232 describes a process for the treatment of milk serum to obtain foam products, said process consisting of a precipitation of a part of the proteins at a pH of 3.0 to 4.7 and at a temperature of 65.degree. to 95.degree. C. by the addition of a nontoxic iron salt such ferric chloride at a concentration comprised between 0.0015 and 0.01 moles/L; the flocculate is rejected and the supernatant liquor serves then for the manufacture of the foam.
The aforementioned processes involve long preparation and in the case of U.S. Pat. No. 2,765,232 the selective precipitation of the proteins is difficult to control.
In addition, tests have revealed that the products obtained by these processes have disagreeable taste and smell, which in the foodstuffs field considerably reduces their attraction for human consumption.
Hence there exists at the present time a need for a process easy and inexpensive to apply, enabling the preparation from milk serum of foam products useful as egg white substitute and possessing substantially the organoleptic properties of the latter.